Method and apparatus for cooling and dehumidifying air

ABSTRACT

The invention relates to a method for conditioning air by means of a ventilation system, in which in order to set a specified target air state characterized by air humidity and air temperature, air having an initial air state is cooled and optionally dehumidified with the aid of an air cooler ( 10 ), by a coolant supply apparatus assigned to the air cooler ( 10 ) for a coolant supplied to the air cooler ( 10 ) regulating both a coolant mass flux and a coolant inlet temperature in accordance with the initial air state and the specified target air state. Moreover, the invention relates to an apparatus for air conditioning is provided.

FIELD OF TECHNOLOGY

The invention relates to a method and an apparatus for cooling anddehumidifying air.

BACKGROUND

Ventilation systems for workplaces and meeting rooms are frequently usedfor maintaining not only the air quality of the room, but also thethermal comfort level. To this end these systems are typically equippedwith system components such that admit at least three thermodynamic airtreatment processes can be carried out: heating, cooling anddehumidification. The systems must be regulated and controlled in such amanner that both objectives (maintenance of the quality and thermalcomfort level) are achieved, although widely varying thermal loads andairborne substances may be present in the room, and for the peoplepresent in the room a fresh-air mass flow necessary for reasons ofhygiene must be maintained.

The comfort range in air-conditioned workplaces is defined with respectto the temperature and the air humidity. Thus in the applicable standardof 2006, DIN EN ISO 7730, the operative temperature for the cooling modefor offices of Category B is specified in a range of 24.5° C.±1.5 K. Formoisture content for the summer months DIN EN 13779 of 2007 proposes arange between 6 and 12 g/kg.

For reasons of energy conservation and reduction in operating costs, theroom air temperature and the relative humidity should be managed overthe year according to a programme of target values, which specifieshigher values for the room air temperature in summer and also highervalues for the relative humidity than in winter. This tracked operationallows the seasonally determined cooling and moisture loads to be takeninto account.

The thermodynamics of the humid air is referred to as psychrometry. Theair in this case represents a gas-vapour mixture, in which the termvapour refers to the component which can condense either as a liquid ora solid in the temperature and pressure range. The remaining componentsare grouped together to form the component group “Gas” and remainunchanged in terms of their quantity for the relevant temperature range.

In the temperature and pressure range occurring in process and roomventilation engineering, moist air can be regarded as a mixture of idealgases. Since at the given temperature non-arbitrary quantities of vapourmix with the non-condensing gas, three states are distinguished. In theunsaturated state, only the gas phase is present. The partial pressureof the vapour is less than the saturation pressure of the vapour in themixture. In the saturated state the partial pressure of the vapourcorresponds exactly to the saturation pressure of the vapour in themixture. The gas phase and beginning condensate phase have the sametemperature T (thermal equilibrium) and the same total pressure(mechanical equilibrium). In the oversaturated state the gas andcondensate phase are present. In the gas phase the relationships of thesaturated state apply.

To represent the air states of moist air and the state changes, variousdiagrams are used. The best known diagrams are the Mollier diagram(Europe) and the Carrier diagram (America). In the case of Mollier theenthalpy (h_(1+x)) of the mixture is chosen as the ordinate and themoisture content x as the abscissa. The enthalpy depends linearly on thetemperature both for the unsaturated region and for the oversaturatedregion. FIG. 1 shows a schematic representation of a simplified Mollierdiagram for a given total pressure.

The cooling and the dehumidification of the air in central ventilationsystems is effected typically by means of air coolers which arepermeated by a coolant. The power is regulated either on the air side orcoolant side by means of a suitable hydraulic circuit. In the case ofhydraulic power regulation, this is typically implemented by variationof the coolant flow at constant coolant feed temperature(quantity-regulated cooling). Less frequently, a regulation option knownfrom heating engineering is used, in which the coolant feed temperatureis regulated by means of intermixing with the coolant return(mixture-regulated cooling).

This results in two different hydraulic circuits for the hydraulicregulation of the cooling power, which also induce different changes ofstate in the air during the permeation of the heat exchanger (aircooler). One of these is a system in which the air cooler is providedwith a quantity regulation system. At a constant coolant feedtemperature the quantity of coolant supplied to the air cooler isregulated. Alternatively, systems are known in which the air cooler isprovided by mixture regulation. In this case the feed temperature of thecoolant fed into the air cooler is regulated.

In a quantity-regulated air cooler, for a water vapour loading above athreshold which is dependent on the feed temperature of the coolantamong other things, a dehumidification always takes place in the coolingmode, since the coolant feed temperature, regardless of the cooling loadof the building, can be assumed to be constant (cf. FIG. 2, line 1-4).Consequently the surface temperature of the air cooler at the coolantintake is close to the feed temperature of the cold water provided bythe cooling unit. Typically this feed temperature is approximately 6° C.in conventional systems. The end point of the change of state of themixed partial currents of the air lies theoretically on the connectingline between the state point of the air flow upstream of the cooler(point 1 in FIG. 2) and the effective surface temperature of the aircooler (point t_(O,eff) in FIG. 2). For a given cooler construction thegradient of the state change in the Mollier diagram for each initialpoint of the moist air therefore depends only on the initial pointitself and on the effective surface temperature of the air cooler (pointt_(O,eff) in FIG. 2).

In this known circuit type two operating modes can be differentiated.Either, the desired level of the dehumidification determines the airoutput temperature from the air cooler, or the cooling requireddetermines the dehumidification level of the air. The desired end pointfor temperature and humidity cannot therefore be set with absoluteprecision with the air cooler alone. In order to obtain a specific airstate, the air flow downstream of the air cooler must therefore eitherbe heated (dehumidification determines the cooling), or the air flowmust be humidified (cooling determines the dehumidification).

With a mixture-regulated air cooler an air flow is fully cooled withoutdehumidification, if the inlet temperature of the coolant medium intothe air cooler does not fall below the dew-point temperature of themoist air (cf. FIG. 2, line 1-2). Only when the coolant feed temperatureis below the dew-point temperature of the moist air, due to restrictionof the coolant return mixture, does condensation of water vapour occur,that is to say, dehumidification for a partial flow of air, (cf. FIG. 2,line 2-3).

In idealised terms, the result is that with permanent coolant mass flowthe entire mass flow of air must be cooled as far as the dew-point,before the dehumidification process can begin at all. According to thisconception, if water vapour condenses out of the mass flow of air, thenthe entire quantity of air must be cooled to the dew-point of thedesired moisture content, which typically results in an under-cooling ofthe air mass flow and is consequently unfavourable from an energy pointof view (cf. FIG. 2, points 3 and 4). The necessary heating of thesuper-cooled air mass flow requires additional energy, which means thecost-effectiveness of a mixture-regulated cooler is further degraded.

To regulate the power of the air cooler each of the two known circuitschanges exactly one variable of the coolant flow. In thequantity-regulated circuit it is the mass flow (the quantity) that isregulated. In the mixture-regulated circuit the coolant feed temperatureis regulated according to the power requirements. To achieve a desiredair state with regard to temperature and water vapour content, bothknown circuits have advantages and disadvantages. In the case of thequantity-regulated air cooler, either post-heating of the air flow orhumidification of the air may be necessary, depending on the air statedesired. In the case of a mixture-regulated air cooler, indehumidification mode deeper cooling is almost always needed than isrequired by the cooling load. The operation of a post-heater istherefore absolutely necessary, in order to obtain the desired airstate.

SUMMARY

The object of the invention is to specify a method and an apparatus forcooling and dehumidifying air by means of a ventilation system, whichenables an accurate and energy efficient setting of a target air statecharacterized by air humidity and air temperature.

This object is achieved according to the invention by a method forcooling and dehumidifying air according to the independent Claim 1 andan apparatus for air conditioning according to the independent claim 7.Advantageous configurations of the invention are the subject matter ofdependent claims.

According to one aspect of the invention, a method for cooling anddehumidifying air is created by means of a ventilation system, in whichin order to set a specified target air state characterized by airhumidity and air temperature, air having an initial air state is cooledand optionally dehumidified with the aid of an air cooler, by a coolantsupply apparatus assigned to the air cooler for a coolant supplied tothe air cooler regulating both a coolant mass flow and a coolant inlettemperature in accordance with the initial air state and the specifiedtarget air state.

According to a further aspect of the invention, an apparatus for coolingand dehumidifying air is created, which comprises the followingfeatures: an air cooler which is configured, in order to set a specifiedtarget air state characterized by air humidity and air temperature, tocool and optionally dehumidify air with an initial air state, and acoolant supply apparatus connected to the air cooler for a coolant to besupplied to the air cooler, which is configured to regulate both acoolant mass flow and a coolant inlet temperature in accordance with theinitial air state and the specified target air state.

With the aid of the proposed techniques, air conditioning, in particularroom air conditioning, is achieved.

Air coolers with conventional hydraulic circuits, when in cooling mode,are only capable of setting desired air states in a limited manner Knownquantity-regulated air coolers are energy-inefficient when the desiredcooling performance leads to an unnecessarily high dehumidificationperformance. By contrast, mixture-regulated air coolers always wastecooling energy when, in addition to pure cooling performance,dehumidification becomes necessary. With the invention, thesedisadvantages are now overcome. In the proposed method and in theapparatus, a precise regulation of air cooling and dehumidification isperformed in a combined manner in the coolant supply apparatus. Both thequantity and the inlet temperature of the coolant for the air cooler areregulated in the coolant supply apparatus. This facilitates a precisesetting of a desired target air state in an energy-efficient manner.

A preferred embodiment of the invention provides that the regulation ofthe coolant mass flow and of the coolant inlet temperature is carriedout with the aid of a hydraulic circuit of the coolant supply apparatus.

In an advantageous embodiment of the invention the regulation of thecoolant mass flow and the coolant inlet temperature is carried out withthe aid of an integrated regulator circuit forming part of the coolantsupply apparatus, in which a mixture-regulated circuit is formed with afeed-quantity regulated pumping apparatus. In this embodiment anintegrated regulator circuit is formed which represents an integrationof the mixture-regulated circuit and the quantity-regulated circuit. Thecoolant supplied to the air cooler is determined by the feed-quantityregulated pump with regard to the quantity (coolant mass flow) and bythe coolant return mixture with regard to temperature.

An advantageous embodiment of the invention provides that the regulationof the coolant mass flow and the coolant inlet temperature is carriedout using a series connection of a mixture-regulated and aquantity-regulated circuit which forms part of the coolant supplyapparatus. It can be provided that the coolant supply apparatus consistsonly of the mixture-regulated and the quantity-regulated circuit.

In one embodiment of the invention it can be provided that theregulation of the coolant mass flow and the coolant inlet temperature iscarried out with the aid of an integrated regulator circuit forming partof the coolant supply apparatus, in which a pump device with constantfeed pressure and a valve regulation device are formed.

A preferred embodiment of the invention provides that the regulation ofthe coolant mass flow and the coolant inlet temperature is carried outwith the aid of an integrated regulator circuit forming part of thecoolant supply apparatus, in which a pump device with constant rotationrate and a bypass device is formed. The bypass device preferablycomprises a regulated bypass.

BRIEF DESCRIPTION

The invention is described in detail in the following by way ofpreferred embodiments with reference to the figures. The figures show:

FIG. 1 a schematic view of a known Mollier diagram for a specified totalpressure,

FIG. 2 a schematic view of the known change of state from moist air whencooling occurs,

FIG. 3 a schematic view of an apparatus for cooling and dehumidifyingair, having an integrated hydraulic circuit consisting of amixture-regulated circuit with a pump device that is directlyfeed-quantity regulated,

FIG. 4 a schematic view of an apparatus for cooling and dehumidifyingair, having an integrated hydraulic circuit consisting of amixture-regulated circuit with a pump device that is indirectlyfeed-quantity regulated,

FIG. 5 a schematic view of an apparatus for cooling and dehumidifyingair having an integrated hydraulic circuit consisting of amixture-regulated circuit with an unregulated pump device with regulatedbypass,

FIG. 6 a schematic view of an apparatus for cooling and dehumidifyingair having an integrated hydraulic circuit consisting of a seriescircuit composed of a mixture-regulated circuit with an unregulated pumpdevice and a quantity-regulated circuit,

FIG. 7 Symbols for elements of the system diagram in FIG. 3 to 6 andFIG. 8

FIG. 8 a simplified system diagram of an air-only system with waste heatrecovery and a circulating air path, wherein a humidification processtakes place by means of a vapour humidifier,

FIG. 9 a schematic view of a regulation strategy for the apparatuses forcooling and dehumidifying air in FIGS. 3 to 6 in the simplified Mollierdiagram,

FIG. 10 a simplified regulation scheme for the hydraulic circuitaccording to FIG. 3

FIG. 11 another simplified regulation scheme for the hydraulic circuitaccording to FIG. 3

FIG. 12 another simplified regulation scheme for the hydraulic circuitaccording to FIG. 3

FIG. 13 another simplified regulation scheme for the hydraulic circuitaccording to FIG. 3, and

FIG. 14 another simplified regulation scheme for the hydraulic circuitaccording to FIG. 3.

DETAILED DESCRIPTION

FIG. 3 shows a schematic view of an apparatus for conditioning air(cooling and dehumidification) having an integrated regulator circuit,in which a feed-quantity regulated pump device is integrated into amixture-regulated circuit. The integrated circuit is embodied in theexemplary embodiment shown as a hydraulic circuit, which can also bereferred to as an “Optimized Dehumidification Control Loop” (OpDeCoLo),which enables the accurate setting of a target air state characterizedby air humidity and air temperature with the aid of a liquid-cooled aircooler with the least possible energy input (cooling and pumpingenergy).

In the apparatus in FIG. 3 a coolant supply apparatus 11, which isformed with a mixing valve 12 and a rotation-speed regulated pump 13, iscoupled to an air cooler 10. The mixing valve 12 connects a cold waterfeed 14 provided by a cooling unit (not shown) with the intermixture ofa coolant return 15 to the coolant feed 16 to be fed into the air cooler10 at the desired temperature and quantity. The state of the airemerging from the air cooler 10 is recorded by means of a temperaturemeasuring device 17 and an air humidity measuring device 18.

The circuit in FIG. 3 corresponds to the mixture-regulated circuit, butin which instead of a pump with constant feed quantity, therotation-speed regulated pump 13 is installed. The mixing valve 12,which defines three paths, is fitted with an actuator 19.

The rotation speed regulation of the rotation-speed regulated pump 13(cf. FIG. 3) can be effected with the aid of a frequency converter (notshown). In the case where dry cooling is desired, the air cooler 10 andthe coolant mass flow are designed such that the cooling power isdelivered at a coolant inlet temperature above the respective dew-pointof the moist air. In many cases this requires a larger air cooler thanin the case of a quantity-regulated hydraulic circuit or amixture-regulated circuit with wet cooling.

Alternatively to this, either a pump 40 with constant feed pressuretogether with a regulated straight-way valve 41 (cf. FIG. 4) or a pump50 with constant rotation rate with a bypass 51 (cf. FIG. 5) can beprovided, which is preferably regulated. Expressed in very simplifiedterms the dehumidification of the air is specified by the selection ofthe cold water inlet temperature, while the cooling power is specifiedby means of the coolant mass flow. The respective total cooling powerdelivered by the cooling and dehumidification of the air cooler 10 istherefore given as a combination of the coolant mass flow and coolantinlet temperature.

With the proposed circuits, state changes can be achieved which can alsobe implemented in a different embodiment with a series circuit formedfrom a quantity-regulated and a mixture-regulated circuit element (cf.FIG. 6), but with markedly reduced energy expenditure. FIG. 6 shows aschematic representation of an apparatus for conditioning air (coolingand dehumidification) having an integrated regulator circuit, consistingof a series circuit formed of a mixture-regulated circuit 60 with anon-feed quantity regulated pumping device 61 and a quantity-regulatedcircuit 62. In FIG. 6 equivalent features are assigned the sanereference labels as in FIGS. 3 to 5.

From an energy point of view the quantity-regulated air cooler whendehumidification is required is very much more efficient than themixture-regulated air cooler. The economy potential of the airconditioning apparatus according to FIGS. 3 to 6 relative to the knownquantity-regulated air cooler is obtained in particular for thefollowing cases:

-   -   For all initial air states which require cooling and of which        the moisture content is less than the maximum moisture content        in the target state, for example for reasons of comfort, and the        dew-point of which is above the coolant inlet temperature of a        conventional quantity-regulated hydraulic circuit. Precisely in        this area, in which for reasons of comfort no dehumidification        is required, a mixture-regulated air cooler would be more        favourable from an energy point of view than a        quantity-regulated air cooler.    -   For initial air states, the moisture content of which is above        the maximum air humidity in the target air state. Here the        difference between the moisture content of the initial air state        and the maximally permitted moisture content and the temperature        of the target area are key factors in determining the potential        for economies. In the case of the quantity-regulated circuit,        initial air states with high air temperature but low        dehumidification load typically lead to an excessive        dehumidification.

By contrast, initial states with high moisture content but where thereis only a small temperature difference relative to the target area, leadto an under-cooling of the air mass flow with all hydraulic circuits,which needs to be compensated by post-heating.

Below, the effects of the hydraulic circuit of the air cooler on thespecific cooling energy demand are examined for a ventilation system.

For the comparison an air-only system (cf. FIG. 8) with recuperativewaste heat recovery and air recirculation controller (Economizer Mode)was chosen. The economy potential of the air conditioning apparatusaccording to FIG. 3 is related both to the mixture-regulated and thequantity-regulated air cooler. For simplicity, any energy requirementsappropriate to post-heating or humidification are not considered in thiscomparison, a fact which reduces the calculated potential economyrelative to the actual case.

A air-only system with regenerative waste heat recovery (WRG) and arecirculated air valve controller corresponds to the state of the artfor ventilation systems which have to dissipate high thermal loads underconditions of varying levels of human occupancy. For this comparison acombined heat-/cooling recovery system was chosen for the heat recovery,which can be easily bypassed as required by switching off the pump andfurthermore offers the facility to guide the external air flow andoutgoing air flow in a spatially separate manner Available systems arefrequently retrofitted with such systems.

TABLE 1 Boundary conditions for determining the energy required for aircooling according to the hydraulic circuit of the air cooler. IdentifierValue Room air temperature 25° C. Room air loading 1 g/kg above outsideair Air heating by ventilators 1K in each case Air temperature after aircooler (target) 18° C. Loading after cooler (target) 6 to 10 g/kgRecovered heat figure WRG 0.5 Recirculated air proportion 0 or 50%Coolant feed temperature 6° C. Coolant return temperature 12° C.

The ventilation system is to be operated such that in summer the WRG isonly active when the temperature of the outside air (ODA) exceeds thatof the outgoing air (EHA). The pre-treated outside air (PODA) after theWRG is then intermixed with recirculated air (RCA) in the mixing chamberonly when the recirculated air has a lower temperature than thepre-treated outside air flow (PODA). The moisture content of therecirculated air has been assumed to be in each case 1 g/kg higher thanthat of the outside air, on account of sources of moisture in the room.The boundary conditions of the comparison are set out in Table 1.

The intermixture of recirculated air reduces not only the temperaturereduction to be provided by the air cooler, but also decreases thedifference between the moisture content of the outside air and thetarget value after the air cooler.

The calculation of the air states that apply after the air cooler isbased on simplified methods. For the mixture-regulated air cooler, itwas assumed that the cooling process takes place until the dew-pointtemperature is reached without condensate being produced. In the case ofadditional cooling the change of state follows the saturation line. Inthe case of the quantity-regulated air cooler it was assumed that thechange of state in each case lies on a straight line between the initialpoint and a temperature proportional to the effective surfacetemperature of the cooler t_(O,eff). The air-conditioning apparatusaccording to FIG. 3 creates a combination of both types of circuit,wherein in the boundary region either a mixture-regulated or aquantity-regulated cooler is present.

FIG. 7 shows symbols for elements of the system diagram in FIGS. 3 to 6and FIG. 8. Here an air-only system with heat recovery and recirculatedair path is shown in simplified form, wherein a humidification processtakes place by means of a vapour humidifier.

Although FIG. 8 shows a complete air-only system, the estimation of theenergy economising potential only includes the cooling energy demand(air cooling and dehumidification). Neither post-heating norhumidification power is taken into account in this comparison. Also notconsidered were the energy costs for operating the pumps. Here also thehydraulic circuit shown in FIG. 3 performs better than the two basecircuits and the circuits of FIGS. 4 to 6.

For the present system type the cooling energy demand for threehydraulic circuits was examined for different German climates. For thispurpose, statistical weather data from 2003 according to DIN 4710 waschosen for the outside air values and the annual specific cooling energydemands were compared with one another. The results for Mannheim aresummarised below (cf. Table 2).

TABLE 2 Specific annual cooling energy demand for an air mass flow of 1kg/h for climate data for Mannheim Annual cooling energy demand n termsof the Daily operating mixture-regulated cooler in % time of themixture-regulated quantity-regulated A/C system cooler cooler OpDeCoLo24 h 100 96 90 (0 to 24 hours) 12 h 100 98 90 (6 to 18 hours)

Under the assumptions made for the boundary conditions the superiorityof the OpDeCoLo relative to the conventional circuits is clearly shown,because dehumidification is only used when this is really necessary forreasons of comfort.

To realise the savings potential, with regard to hardware in one of theembodiments described above a rotation-speed regulated pump is used. Thedesign of an associated regulation technique which not only adjusts thecoolant mass flow or the coolant inlet temperature, but also therespective optimum composed of the coolant inlet temperature and coolantmass flow, is described below. The rotation speed regulation of the pumpcan be effected either by a frequency converter (cf. FIG. 3) or, asshown in FIG. 4, by varying the flow resistance with the aid of a valve.The hydraulic circuits of FIG. 5 and FIG. 6 with unregulated pumpdevices are also capable of achieving the cooling energy economyaccording to Table 2, but are characterized by higher pumping energycosts.

FIG. 9 shows a schematic representation of a regulation strategy for thepreviously described air coolers in a simplified Mollier diagram. Unlikein conventional regulator circuits of air coolers, in the circuitsproposed here both the coolant quantity and also their inlet temperatureare always regulated.

Below, the regulation design is described in more detail.

In the case of cooling without dehumidification the surface temperatureof the cooler must not at any point be equal or below the dew-pointtemperature of the moist air to be cooled. Therefore, in this case thefeed temperature of the coolant fluid for the air cooler must not fallbelow the dew-point temperature of the moist air. Since the coolingpower depends on the mean surface temperature of the air cooler, the aircannot be cooled down as far as the saturation line. Therefore the aircooler in this case is operated at a higher pump rotation rate, whereinthe power matching is effected by varying the coolant return mixture.

With regards to the coolant it follows that:

{dot over (Q)} _(cooling) ={dot over (m)} _(coolant) *c _(p)_(Kühlmittel) *(t _(return) −t _(flow))  (1)

with

-   {dot over (Q)}_(cooling) cooling power of the air cooler [W]-   {dot over (m)}_(coolant) coolant mass flow [kg/s]-   c_(pcoolant) specific heat capacity of the coolant [kJ/(kg*K)]-   (t_(return)−t_(flow)) Temperature difference of the coolant upstream    and downstream of the air cooler [K]    and t_(flow)≧t_(dew-point)

With regards to the air the cooling power is determined according toequation (3), making use of equation (2):

Δh _(cooling)=(x ₁*(r ₀ +c _(p) _(D) *t ₁)+c _(p) _(L) *t ₁)−(x _(LK)*(r₀ +c _(p) _(D) *t _(LK))+c _(p) _(L) *t _(LK))  (2)

with

-   r₀ latent heat of water at 0° C. [kJ/kg]-   c_(pD) specific heat capacity of the water vapour [kJ/(kg*K)]-   c_(pL) specific heat capacity of the dry air [kJ/(kg*K)]

{dot over (Q)} _(cooling) ={dot over (m)} _(air) *Δh _(cooling)  (3)

with

-   {dot over (m)}_(air) air mass flow [kg/s]-   Δh_(cooling) Enthalpy difference; here at constant moisture content    of the air [kJ/kg]

In the case of cooling with dehumidification, as well as the air outlettemperature from the cooler the water vapour content of the air is alsoregulated. To do so, both the pump rotation speed and the coolant returnmixture are modified such that the target point of the air at the cooleroutlet is achieved. The feed mass flow (pump rotation rate) takes overthe quantity regulation and the coolant inlet temperature (coolantreturn mixture) the mixture regulation. Expressed very simply, thepumping mass flow at constant coolant temperature determines thegradient of the change of state in the Mollier diagram; at constantpumping flow the coolant inlet temperature determines the sensiblecooling power. However, the two parameters are not independent of eachother, since due to the influence on the coolant return temperature whenthe coolant inlet temperature and the pumping mass flow changes, theeffective surface temperature changes—which has an effect both on thesensible cooling power and the dehumidification of the air flow. For aspecified outlet air state there is exactly one combination of pumpingmass flow and coolant inlet temperature corresponding to the initialstate.

FIGS. 10 to 14 show simplified regulation schemata for the hydrauliccircuit according to FIG. 3. The letters “R” and “N” refer to a returnmixture and a pump rotation rate regulation. Arrows indicated inconnection with these control variables show a regulation towards anincrease (arrow upwards) or towards a decrease (arrow downwards) of therespective variable. The variables T_(target) and T_(actual) refer to atarget and an actual temperature of the cooled/de-humidified air. In thesame way X_(target) and X_(actual) refer to a target and an actual airhumidity. The numbers “11”, “21”, . . . are used for reference among theregulation schemata in FIGS. 10 to 14.

The features of the invention disclosed in the present description,claims and the figures can be of significance both individually and inany desired combination for the implementation of the invention in itsvarious embodiments.

1. Method for conditioning air by means of a ventilation system, inwhich in order to set a specified target air state characterized by airhumidity and air temperature, air having an initial air state is cooledand optionally dehumidified with the aid of an air cooler, by a coolantsupply apparatus assigned to the air cooler for a coolant supplied tothe air cooler regulating both a coolant mass flow and a coolant inlettemperature in accordance with the initial air state and the specifiedtarget air state.
 2. The method according to claim 1, wherein theregulation of the coolant mass flow and of the coolant inlet temperatureis carried out with the aid of a hydraulic circuit of the coolant supplyapparatus.
 3. The method according to claim 1, wherein the regulation ofthe coolant mass flow and the coolant inlet temperature is carried outwith the aid of an integrated regulator circuit forming part of thecoolant supply apparatus, in which a mixture-regulated circuit with afeed-quantity regulated pumping device is formed.
 4. The methodaccording to claim 1, wherein the regulation of the coolant mass flowand the coolant inlet temperature is carried out with the aid of aseries circuit of a mixture-regulated and a quantity-regulated circuitforming part of the coolant supply apparatus.
 5. The method according toclaim 1, wherein the regulation of the coolant mass flow and the coolantinlet temperature is carried out with the aid of an integrated regulatorcircuit forming part of the coolant supply apparatus, in which a pumpdevice with constant feed pressure and a valve regulation device areformed.
 6. The method according to claim 1, wherein the regulation ofthe coolant mass flow and the coolant inlet temperature is carried outwith the aid of an integrated regulator circuit forming part of thecoolant supply apparatus, in which a pump device with constant rotationrate and a bypass device are formed.
 7. Apparatus for conditioning air,having: an air cooler, which in order to set a specified target airstate characterized by air humidity and air temperature is configured tocool and dehumidify air having an initial air state, and a coolantsupply apparatus connected to the air cooler for a coolant to besupplied to the air cooler, which is configured to regulate both acoolant mass flow and a coolant inlet temperature in accordance with theinitial air state and the specified target air state.
 8. The apparatusaccording to claim 7, wherein the coolant supply apparatus is formedwith a hydraulic circuit which is configured to regulate the coolantmass flow and the coolant inlet temperature.
 9. The apparatus accordingto claim 7, wherein the coolant supply apparatus is designed with anintegrated regulator circuit in which a mixture-regulated circuit isformed with a feed-quantity regulated pump device and which isconfigured to regulate the coolant mass flow and the coolant inlettemperature.
 10. The apparatus according to claim 7, wherein the coolantsupply apparatus is designed with a series circuit, in which amixture-regulated and a quantity-regulated circuit are connected inseries.